Backpack



FIG. 1 is a right side perspective view of a backpack, showing my new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a left side elevational view thereof;

FIG. 5 is a right side elevational view thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a bottom plan view thereof.

The broken lines in the photographs are for the purpose of illustrating environment and form no part of the claimed design. The broken lines immediately adjacent the shaded areas represent the boundary of the claimed design. 

CLAIM The ornamental design for a backpack, as shown and described. 